Conventionally, conveying apparatuses for conveyance objects such as baggage to destinations have been available. For example, in an airport, an airport baggage conveying apparatus is used to convey the baggage of passengers to a loading area close to a passenger plane to be boarded by the passengers.
Regarding such an airport baggage conveying apparatus, a large airport, for example, a hub airport having an extended area leads to an extremely long distance from a location for checking the baggage of passengers in a check-in counter to a location where the intended plane is stopped (or a loading area near the location) and a large number of pieces of baggage. Thus, in order to deliver all the baggage to the plane within a limited time before the plane takes off, a conveying speed for the baggage needs to be increased.
As a conventional method of conveying objects such as baggage with high velocity, FIG. 6 shows a conveying method through a conveyance path including a plurality of conveyors (e.g., a belt conveyor or a wheel conveyor). A conveyance object 90 on the conveyance path is first placed on a tray 99 on a first conveyor 91 disposed on the extreme upstream end of the path. The first conveyor 91 conveys the tray 99 bearing the conveyance object 90 with a constant low conveying speed. A second conveyor 92 with a constant speed higher than that of the first conveyor 91 is disposed downstream of the first conveyor 91. Moreover, a plurality of conveyors (with constant speeds) including a high-speed third conveyor 93 and a higher-speed fourth conveyor 94 are provided in series downstream of the second conveyor 92 so as to sequentially increase in conveying speed. The tray 99 bearing the conveyance object 90 is sequentially transferred to these conveyors so as to gradually increase a conveying speed for the conveyance object 90. This can increase the conveying speed of the overall conveyance path. In an area near a destination (e.g., a plane to carry passengers), a plurality of conveyors are provided in series so as to sequentially decrease in conveying speed contrary to the above sequential increase in conveying speed. The tray 99 bearing the conveyance object 90 is sequentially transferred to these conveyors with gradual deceleration.
Japanese Patent Laid-Open No. 9-323810 discloses, as related art, such a conventional conveying apparatus with gradual acceleration and deceleration.
In the gradual acceleration/deceleration method as described above, however, the conveying speed rapidly changes when the tray 99 is transferred to another conveyor. Thus, the conveyance object 90 on the tray 99 receives an inertial force caused by a conveyance acceleration (a change of the conveying speed). When a suitcase is conveyed as passenger's baggage in an airport baggage conveying apparatus, such an inertial force may cause an impact to the content of the suitcase or shift the position of the suitcase on the tray 99. Thus, passengers' baggage may be insufficiently maintained or less smoothly conveyed.
For example, in the case of a belt conveying apparatus, when the conveying speed rapidly changes during the transfer of the tray 99 over the conveyors, a slip may occur between the tray 99 and the belts of the conveyors. Thus, repeated conveyance may wear the belts and the tray.
In order to solve the above problems, in the invention of Japanese Patent Laid-Open No. 9-323810, a conveyor shaft having a spiral groove is rotated with a returnable case engaged with the spiral groove, achieving continuous acceleration and deceleration.
However, if such a configuration is installed in an extended area of a large airport, the conveyor shaft having the spiral groove, which is a member for the configuration, needs to be provided over a long path. Moreover, the returnable case needs to be specially designed for engagement with the spiral groove. This may extremely increase the introduction cost. Furthermore, the complicated configuration leads to low reliability and difficulty in maintenance. During acceleration of the returnable case using the conveyor shaft, the subsequent returnable case cannot be transported from upstream of the conveyor shaft to the section of the conveyor shaft. The subsequent returnable case cannot be transported to the section of the conveyor shaft until the preceding returnable case has been transported to finish acceleration and then the conveyor shaft is decelerated to the original speed. Thus, the conveyance efficiency cannot be sufficiently improved.
An object of the present invention is to provide a conveying apparatus that increases the conveying speed of a conveyance object over an overall conveyance path without causing an impact and a displacement of the conveyance object, and sufficiently improves reliability conveyance efficiency at low cost.